The present invention relates to the field of bypass turbojets, and more particularly to afterburner devices of such jets.
In a bypass turbojet with an afterburner, having an after-body of the type shown in FIG. 1, the air stream is initially sucked in by a low pressure compressor. A first portion of the air stream at the outlet from the low pressure compressor feeds a high pressure compressor, while a second portion passes into a first passage 1 defined between an external annular casing 2 and a first internal annular casing 3. The air stream compressed by the high pressure compressor feeds a combustion chamber, which in turn feeds combustion gas to a high pressure turbine followed by a low pressure turbine, which has an outlet passing via a second passage 4 defined between the first internal annular casing 3 (or confluence sheet) and a second internal annular casing 5 (or exhaust cone). The combustion gas feeding the second passage 4 is at high temperature and is referred to as a “primary” stream (or hot stream). The air feeding the first passage 1 presents a temperature that is substantially lower than the temperature of the primary stream and is referred to as a “secondary” stream (or cold stream).
Downstream from the outlet of the turbine it is possible to increase thrust by injecting an additional quantity of fuel into the primary and secondary streams, with the fuel burning within an afterburner channel. Such a system mainly comprises a set of devices 8, referred to as “flame-holders”, and a burner ring 6. The burner ring 6 is carried by the flame-holder devices 8 and is located in the secondary stream, in the vicinity of the confluence sheet 3.
A portion of the injection takes place via the burner ring 6 that serves to inject a portion of the fuel in uniform manner and to stabilize the flame.
The structure of a flame-holder device 8 is shown in FIGS. 2 and 3. The flame-holder device 8, which is described in Document US 2011/0138773, comprises an arm 80 in the form of a channel-section trough (which section may be V-shaped or U-shaped) with its web facing upstream relative to the gas flow direction, a ventilation tube 81, a tubular fuel injector 82, and a heat shield 83 in the form of a curved metal sheet having its concave side facing downstream.
The flame-holder device 8 also has an adapter part 84 (FIG. 3) comprising a base or plate 840 from which there extend two fastener legs 841 and 842, a first fastener support 843 for fastening the external portion of the burner ring 6 extending between the two legs 841 and 842 level with their central branches, and a guide element 844 having two holes 8440 and 8441 through which there pass respectively the fuel injector 82 and the ventilation tube 81 that are mounted on the legs 841 and 842, the guide element 844 also having a second fastener support 845 for fastening the internal portion of the burner ring and including a hole 8442 through which fastener means (not shown in FIG. 2) pass for fastening the internal portion of the burner ring 6.
The adapter part 84 serves to position and fasten the arms in the flow passage, the base 840 being fastened to the internal wall of the external casing 2 (FIG. 1), while the arm 80 is fastened to the legs 841 and 842 by fastener members of the rivet or bolt type, via fastener holes 8410 and 8420 present in the fastener tabs and the holes 801 present in the arm 80.
In addition to positioning and holding the arm 80, the adapter part 84 performs several other functions, namely:                taking off static pressure from the secondary air stream via the two legs 841 and 842, each of which has its inside constituted by a hollow cavity 841a and 842a that leads into a top cavity 840a formed in the base 840, a takeoff orifice 8410, 8420 being pierced in the bottom portion of each of the legs 841 and 842 in order to feed the cavity 840a with air;        fastening the burner ring via the first and second fastener supports 843 and 845; and        guiding the ventilation tube by means of the guide element 844.        
Nevertheless, performing all of those functions requires an adapter part that is complex in shape and expensive to make.
Furthermore, the positioning and fastening of the arm by means of the adapter part is not industrial in that it requires each of the parts produced to be matched and fitted.
Finally, another drawback is that at least the plate, the fastener tabs, and the first fastener support for the burner ring are formed integrally in the same piece of metal material obtained by casting, for example. Since the adapter part extends close to a source of heat at high temperature (hot stream), it also needs to be made out of a metal material that withstands high temperatures, and that is therefore expensive.